Preheat oven to 425°F.
Combine 1 cup flour, undissolved yeast, sugar and salt in a large bowl. Heat water and butter until very warm (120° to 130°F) and add to flour mixture. Beat until well blended, about 1 minute. Gradually add enough remaining flour to make a soft dough. Dough should form a ball and will be slightly sticky. Knead** on a floured surface, adding additional flour if necessary, until smooth and elastic, about 4 minutes.
Pat dough with floured hands to fill greased pizza pan OR roll dough on a floured counter to 12-inch circle; place in greased pizza pan. Dough can also be pated or rolled to fit a greased 15 x 10-inch jelly roll pan (great for serving a crowd.) Form a rim by pinching the edge of the dough.
Beat cream cheese, sour cream and garlic powder in a small bowl until creamy. Spread over crust. Sprinkle with cheese and top with jalapenos. Bake on lowest oven rack for 14 to 18 minutes (15 to 20 minutes for jelly roll pan), until cheese is bubbly and crust is browned.
*If you don’t have a thermometer, water should feel very warm to the touch.
**To knead the dough, add just enough flour to the dough and your hands to keep the dough from sticking. Flatten dough and fold it toward you.Using the heels of your hands, push the dough away with a rolling motion. Rotate dough a quarter turn and repeat the “fold, push and turn” steps. Keep kneading dough until it is smooth and elastic. Use a little more flour if dough becomes too sticky, always working the flour into the ball of dough.